And the data shows that 2012 was a record year – for all the wrong reasons. Thomas Karl, director of the NOAA’s National Climatic Data Center, said: “In 2012 practically every variable we had broke a record. But there’s a lot of variability in the climate system year to year, and that’s the importance of this work – to put a year’s data in its historical context.”

Greenhouse gases are rising, not falling.NOAA

Record levels of greenhouse gases were pumped into the atmosphere, with CO2 levels approaching 400ppm, something not seen on Earth for 800,000 years. Methane and nitrogen oxide levels have also increased, with the cumulative warming effect on the atmosphere increasing by 32% since 1990. Overall, 2012 was among the top 10 warmest years since 1958.

The average sea level was 3.5cm above the average since satellite records began in 1993, with sea levels rising around 2.8-3.5mm per year. Oceanic heat levels, which have been steadily rising, in some areas reached as high as 4 gigajoules/sq m. That’s enough energy per square meter of water to power a 100W lightbulb for almost a year.

The planet’s oceans keep getting warmer.NOAA

But it is the Arctic that has seen some of the most severe changes. Jackie Richter-Menge, a research civil engineer and cold regions specialist from the US Army Corps of Engineers, said: “The Arctic continues to be a region where we have some of the most compelling evidence of warming temperatures, where surface temperatures are increasing more than twice the rate of the rest of the world.”

Among the evidence recorded last year was record low snow cover across Eurasia and North America, where the rate of snow cover decline is faster than that of sea ice. Much of this has been attributed to strong, southerly airflows throughout the spring and summer that brought warm air over the Arctic. The extent of sea ice over the Arctic reached a new low of 1.3m square miles, an 18% reduction on projected levels.

And where the ice retreats, plants now grow, as Richter-Menge explained: “The drastic and persistent reduction in summer sea ice cover can be linked to the growth of vegetation. These are no longer anomalies or exceptions, but the norm that we expect to see, and which looks set to continue for the future.”

Kathryn Sullivan, NOAA Administrator, said it was up to policy makers to draw lessons from the report. “This is the ‘new normal’. Many of the models that infrastructure planning relies on assume the future will be like the past, but the trends we see here should lead us to question whether that will be the case,” she said.

Thomas Karl said: “It’s critical to compile a picture of Earth’s changing climate, so every year we try and address further data as we improve our technological ability to record additional measurements.” Some surface and ocean measurements go back to the mid-19th century, many date to the use of weather balloons and aircraft measurements in the 1950s, and others from the start of satellite recordings in the 1970s.

“The report does not try to explain what we’re seeing; this report is focused on the data,” he added. “But all the signs are of a warming world.”

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